Paving the way for a Hepatitis C Virus vaccine

HCV remains a major global health burden, with limited access to treatment and a high reinfection risk, underscoring the need for a vaccine. In this thesis critical challenges in Hepatitis C Virus (HCV) research by optimizing methods for studying humoral immune responses and identifying key factors associated with protective immunity are studied.
The first part of the thesis focuses on refining in vitro methodologies to study antibody responses against HCV. First, a CD81 knockout HEK293T cell line was developed to enhance HCV pseudoparticle (HCVpp) infectivity without affecting antibody neutralization sensitivity. Second, a standardized HCVpp neutralization assay was optimized for improved reproducibility and efficiency, and third a globally representative HCVpp panel was established. Finally, a binding antibody multiplex assay (BAMA) and a competition-based variation (BAMCA) were introduced to evaluate antibody specificity and epitope accessibility.
The second part of the thesis investigates immune correlates of protection against reinfection. Analysis of individuals at risk of HCV reinfection revealed that non-reinfected individuals had higher levels of neutralizing and binding antibodies, particularly IgG1 and IgG3. Protection was linked to antibodies targeting the CD81 binding region and enhanced antibody Fc-mediated effector functions, including antibody-dependent phagocytosis, cytotoxicity, and complement activation.
This research advances the knowledge on HCV immunology by standardizing methodologies and identifying immune features essential for vaccine development. The findings provide a framework for designing protective immunization strategies and contribute to global HCV elimination efforts.